The present invention relates to a vehicle steering apparatus in which the steering characteristics of the vehicle can be altered by the control of an actuator.
There are vehicle steering apparatuses in which the steering characteristics can be altered by the control of a steering actuator. Such steering apparatuses include an apparatus with a so-called steer-by-wire system in which an operating member is not mechanically connected to the wheels of the vehicle, and an apparatus in which an operating member is mechanically connected to the wheels of the vehicle.
In the steering apparatus that employ the steer-by-wire system, without mechanically connecting the operating member having a shape of a steering wheel to the wheels of the vehicle, the steering characteristics are altered by transmitting the movement of the steering actuator to the wheels of the vehicle so that a variation in the steering angle is generated. In the steering apparatus in which the operating member is mechanically connected to the wheels of the vehicle, the rotation of an input shaft corresponding to the operation of the steering wheel is transmitted to an output shaft via a variable transmission ratio mechanism such as a planetary gear mechanism or the like, the rotation of this output shaft is transmitted to the wheels of the vehicle so that a variation in the steering angle is generated, and the steering characteristics are altered by driving the ring gears or the like in the planetary gear mechanism by the steering actuator.
In the steering apparatus that employ the steer-by-wire system, a fail-safe function which is used to steer the wheels of the vehicle in the case of trouble with the actuator or control system is required. Conventionally, a system has been proposed in which a fail-safe function is realized by using a clutch or the like to connect an operating side rotating member that is mechanically connected to the operating member with a vehicle wheel side rotating member that is mechanically connected to the wheels of the vehicle in the case of such trouble in the actuator or control system. However, since the abovementioned operating side rotating member and vehicle wheel side rotating member are not mechanically connected to each other on normal circumstances, the reliability of this function as a fail-safe function is insufficient.
In the steering apparatus in which the operating member is mechanically connected to the wheels of the vehicle via a variable transmission ratio mechanism, the movement of the wheels of the vehicle and the movement of the operating member interfere with each other when control for the purpose of compensating for fluctuations in the steering angle caused by irregularities in the road surface or the like is performed. Accordingly, a smooth operating feeling that is unaffected by irregularities in the road surface or the like, and operation of the operating member without any resistance, are impossible.
It is an object of the present invention to provide a vehicle steering apparatus that can solve the abovementioned problems.
The vehicle steering apparatus of the present invention comprises an operating member, a steering actuator, a steering gear which transmits the movement of the steering actuator to the vehicle wheels so that a variation in the steering angle is generated, a control system which is capable of controlling the steering actuator so that the steering angle varies in accordance with the operation of the operating member, an operating side rotating member which is mechanically connected to the operating member so as to rotate in accordance with the operation of this operating member, a vehicle wheel side rotating member which is mechanically connected to the vehicle wheels so as to rotate in accordance with the variation in the steering angle, and a transmission mechanism which mechanically connects the operating side rotating member and the vehicle wheel side rotating member to each other so that the transmission of rotation is possible, and so that the ratio of the rotational transmission can be varied.
In the present invention, since the operating side rotating member that is mechanically connected to the operating member and the vehicle wheel side rotating member that is mechanically connected to the vehicle wheels are capable of the mutual transmission of rotation via the transmission mechanism, the reliability of the fail-safe function can be improved.
It is desirable that the vehicle steering apparatus of the present invention comprise an adjustment actuator that is used to adjust the ratio of rotational transmission by the transmission mechanism, and a control system which is capable of controlling this adjustment actuator so that the ratio of rotational transmission by the transmission mechanism can be varied.
By using such control of the adjustment actuator to vary the ratio of rotational transmission between the vehicle wheel side rotating member and the operating side rotating member, it is possible to cause rotation of the operating side rotating member without this rotation being affected by the rotation of the vehicle wheel side rotating member. As a result, an arbitrary operating torque can be caused to act on the operating member without being affected by variations in the steering angle, so that steering operation can be smoothly accomplished without any mutual interference between the movement of the wheels of the vehicle and the movement of the operating member. For example, the vehicle steering apparatus of the present invention can comprise means for determining the amount of operation of the operating member, means for storing in memory a set relationship between the amount of operation of the operating member and the target steering angle, means for calculating the target steering angle from the determined amount of operation of the operating member and the stored relationship, means for determining the actual steering angle, means for storing in memory a set relationship between the amount of operation of the operating member and the target operating torque, means for calculating the target operating torque from the determined amount of operation of the operating member and the stored relationship, and means for determining the actual operating torque of the operating member. Furthermore, the abovementioned steering actuator is made controllable so that the deviation between the target steering angle and actual steering angle is reduced, and the abovementioned adjustment actuator is made controllable so that the deviation between the target operating torque and the actual operating torque is reduced. Furthermore, the adjustment actuator can be made controllable so that a torque oriented in an arbitrary direction acts on the operating member. The operating torque that acts on the operating member when the steering angle is varied can be reduced to zero by making the abovementioned adjustment actuator controllable so that the rotational force acting on the operating side rotating member is reduced to zero. Moreover, in cases where a fail-safe system in which the operating member and the vehicle wheels are connected via the abovementioned operating side rotating member and vehicle wheel side rotating member is caused to function when an abnormality in the steering actuator is detected, the torque that is caused to act on the operating member by the adjustment actuator can be controlled.
It is desirable that the vehicle steering apparatus of the present invention comprise abnormality detection means for detecting an abnormality in the adjustment actuator, and a restraining mechanism that is capable of restraining the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member, and that the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is restrained by the restraining mechanism, the driving of the adjustment actuator is stopped, and the steering actuator is controlled so that a steering assist torque is caused to act, in cases where the abnormality is detected in the adjustment actuator.
As a result, the steering apparatus can function as a power steering apparatus in cases where an abnormality is detected in the adjustment actuator.
It is desirable that the vehicle steering apparatus of the present invention comprise abnormality detection means for detecting an abnormality in the adjustment actuator, and a restraining mechanism that is capable of restraining the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member, and that the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is restrained by the restraining mechanism, and the driving of the adjustment actuator and steering actuator is stopped, in cases where the abnormality is detected in the adjustment actuator.
As a result, the steering apparatus can function as a manual type steering apparatus in cases where an abnormality is detected in the adjustment actuator.
It is desirable that the vehicle steering apparatus of the present invention comprise abnormality detection means for detecting an abnormality in the adjustment actuator, and that the driving of the adjustment actuator is stopped, and the transmission of rotation between the operating side rotating member and the vehicle wheel side rotating member is stopped, in cases where the abnormality is detected in the adjustment actuator.
As a result, even if an abnormality occurs in the adjustment actuator, the steering angle can be varied by controlling the steering actuator in accordance with the operation of the operating member, and there is no interference with the operation of the operating member.
It is desirable that the vehicle steering apparatus of the present invention comprise abnormality detection means for detecting an abnormality in the adjustment actuator, a restraining mechanism that is capable of restraining the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member, and a change-over switch for the abnormality handling modes that is used in cases where the abnormality is detected in the adjustment actuator, and that the switching of the abovementioned switch enables selection of one of three modes, i.e., a mode in which the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is restrained by the restraining mechanism, the driving of the adjustment actuator is stopped, and the steering actuator is controlled so that a steering assist torque is caused to act, a mode in which the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is restrained by the restraining mechanism, and the driving of the adjustment actuator and the steering actuator is stopped, and a mode in which the driving of the adjustment actuator is stopped, and the transmission of rotation between the operating side rotating member and vehicle wheel side rotating member is stopped.
As a result, in cases where an abnormality is detected in the adjustment actuator, either a mode in which the steering apparatus is caused to function as a power steering apparatus, a mode in which the steering apparatus is caused to function as a manual type steering apparatus, or a mode in which the steering actuator is controlled in accordance with the operation of the operating member, can be selected.
It is desirable that the vehicle steering apparatus of the present invention comprise abnormality detection means for detecting an abnormality in the steering actuator, and a restraining mechanism that is capable of restraining the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member, and that the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is restrained by the restraining mechanism, the driving of the steering actuator is stopped, and the adjustment actuator is controlled so that a steering assist torque is caused to act, in cases where the abnormality is detected in the steering actuator.
As a result, the steering apparatus can be caused to function as a power steering apparatus by the adjustment actuator in cases where an abnormality is detected in the steering actuator.
It is desirable that the vehicle steering apparatus of the present invention comprise abnormality detection means for detecting an abnormality in the steering actuator, and a restraining mechanism that is capable of restraining the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member, and that the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is restrained by the restraining mechanism, and the driving of the adjustment actuator and the steering actuator is stopped, in cases where the abnormality is detected in the steering actuator.
As a result, the steering apparatus can function as a manual type steering apparatus in cases where an abnormality is detected in the steering actuator.
It is desirable that the vehicle steering apparatus of the present invention comprise abnormality detection means for detecting an abnormality in the steering actuator, and means for detecting a variable that expresses the operating state of the vehicle, and that the driving of the steering actuator is stopped, and the adjustment actuator is controlled so that the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is varied in accordance with the detected variable that expresses the operating state of the vehicle, in cases where the abnormality is detected in the steering actuator.
As a result, even if an abnormality occurs in the steering actuator, the steering apparatus can function as a steering apparatus that is capable of altering the steering characteristics in accordance with the operating state of the vehicle.
It is desirable that the vehicle steering apparatus of the present invention comprise abnormality detection means for detecting an abnormality in the steering actuator, a restraining mechanism that is capable of restraining the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member, means for detecting a variable that expresses the operating state of the vehicle, and a change-over switch for the abnormality handling modes that is used in cases where the abnormality is detected in the steering actuator, and that the switching of the abovementioned switch enables selection of one of three modes, i.e., a mode in which the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is restrained by the restraining mechanism, the driving of the steering actuator is stopped, and the adjustment actuator is controlled so that a steering assist torque is caused to act, a mode in which the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is restrained by the restraining mechanism, and the driving of the adjustment actuator and the steering actuator is stopped, and a mode in which the driving of the steering actuator is stopped, and the adjustment actuator is controlled so that the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is varied in accordance with the abovementioned variable that expresses the operating state of the vehicle.
As a result, either a mode in which the steering apparatus can be caused to function as a power steering apparatus, a mode in which the steering apparatus can be caused to function as a manual type steering apparatus, or a mode in which the steering characteristics can be altered in accordance with the operating state of the vehicle, can be selected in cases where an abnormality is detected in the steering actuator.
It is desirable that the vehicle steering apparatus of the present invention comprise abnormality detection means for detecting an abnormality in the adjustment actuator, abnormality detection means for detecting an abnormality in the steering actuator, and a restraining mechanism that is capable of restraining the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member, and that the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is restrained by the restraining mechanism, and the driving of the adjustment actuator and the steering actuator is stopped, in cases where the abnormality in the adjustment actuator and the abnormality in the steering actuator are detected.
As a result, the steering apparatus can function as a manual type steering apparatus in cases where abnormalities are detected in the adjustment actuator and steering actuator.
It is desirable that the vehicle steering apparatus of the present invention comprise abnormality detection means for detecting an abnormality in the control system of the steering actuator and the adjustment actuator, and a restraining mechanism that is capable of restraining the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member, and that the variation in the ratio of the rotational transmission between the operating side rotating member and the vehicle wheel side rotating member is restrained by the restraining mechanism, and the driving of the adjustment actuator and the steering actuator be stopped, in cases where the abnormality is detected in the control system.
As a result, even if an abnormality occurs in the control system, the steering apparatus can function as a manual type steering apparatus.
It is desirable that the abovementioned transmission mechanism have three elements that are capable of relative rotation, that the ratio of the rotational transmission between two of the elements can be varied in accordance with the variation in the rotational speed of the third element, that one of the three elements is connected to the operating side rotating member, that one of the elements that is not connected to the operating side rotating member is connected to the vehicle wheel side rotating member, that the remaining element is driven by the adjustment actuator, and that the ratio of the rotational transmission is varied by controlling the adjustment actuator by means of the control system. In this case, the abovementioned transmission mechanism has a planetary gear mechanism in which a planetary gear that engages with a sun gear and a ring gear is held by a carrier, and this sung gear, ring gear and carrier can be taken as the abovementioned three elements that are capable of relative rotation. As a result, the transmission mechanism can easily be structured from a known rotational transmission mechanism.
It is desirable that the transmission of rotation between the operating side rotating member and the vehicle wheel side rotating member via the transmission mechanism can be stopped in a state in which a mechanical connection between the operating side rotating member and the vehicle wheel side rotating member is maintained by the transmission mechanism.
As a result, the operating torque can be reduced to zero when there is a variation in the steering angle without any need for the adjustment actuator or control system.
According to the present invention, a fail-safe function can be securely obtained by means of a simple structure, and without any need for lowering the steering feeling experienced by the driver, in a vehicle steering apparatus in which the steering angle is varies by the control of an actuator.